The present invention relates to a process for treating old foundry sand for reuse in place of core sand wherein the precleaned sand grains are subjected to further abrasive-thermal treatment so as to volatize and remove basic constituents adhering to the precleaned sand grains.
Various processes are known for treating old foundry sands. These processes comprise separating the spent additives and their carbonized residuals, etc. from the quartz sand so as to enable one to reuse at least the quartz sand obtained from the processes. These known processes have been catagorized as mechanical reconditioning processes and thermal reconditioning processes. In the mechanical reconditioning processes, certain cleaning of the sand grains is achieved by means of the effect of impact and abrasion. In thermal processes, the binder shells and coatings present on the grains are burnt off.
The success of the aforementioned processes in separating quartz sand and spent binders vary widely as as basic constituents still adhere to and surround the individual sand grains. In addition, the thermal reconditioning processes suffer from the disadvantage that additional waste disposal measures due to the thermal process impose a burden on the environment.
Naturally, it would be highly desirable to provide a process for the reconditioning treatment of old foundry sand wherein the reclaimed sand material can be used as core sand wherein the individual sand grains are freed from the binder fractions and basic constituents so that they no longer have a negative influence on the curing process during the production of the core.
Accordingly, it is the principle object of the present invention to provide a process for treating old foundry sand for recycle in the place of core sand for the production of foundry cores.
It is a further object of the present invention to provide a process as aforesaid wherein the old foundry sand is precleaned in a first stage in a known manner and thereafter further treated so as to volatize and remove the basic constituents adhering to the precleaned sand grains.
Further objects and advantages of the present invention will appear hereinbelow.